I have a hand held GPS that has a " Max Speed" hold feature so I can watch water conditions, tach. and speedo and check after a run to see best speed. Might not be 100% accurate, but give me a idea of performance from run to run. My speedo is with in 1 mph of my GPS so I just use it, and check "Max Speed" on GPS after. Mile's traveled or "Trip" is also a nice feature.